This invention relates to a method and apparatus for controlling static charges, and particularly to a method and apparatus for controlling static induced product seal inclusions in packaging operations involving materials inclined to generate or accumulate static electrical charges.
In machines for packaging dry particulate material such as coffee in plastic film packages, attachment of some of the material to the inside of the plastic film is a problem. This attachment is most often caused by static charges on the film and also static charges on the particulate material as it is injected into the package. The presence of such material clinging to the inside of the film is unsightly, but more importantly prevents a good seal from being effected. Heretofore, conventional static eliminators have been positioned about the outside of the plastic packages to remove the static charge from the film. This has not proven to be satisfactory for two reasons; (1) the static charge must migrate through the film before it can be removed, and (2) there is no practical opportunity to control static on the product itself. Removing the static charge in the conventional manner becomes increasingly difficult with high barrier films or thicker films and with high packaging speeds. Additionally, particulate materials that are being loaded into the plastic packages frequently have a static charge on the individual particles themselves. Static eliminators positioned adjacent to the outside of the film are incapable of removing such static charges.
The present invention is directed to a method and apparatus for overcoming the foregoing problems.